Crash destroys rocket ahead of X Prize contest

Video: The rocket Texel’s crash spewed fuel that ignited and “made a fireball that would make any Hollywood movie proud”, says company founder John Carmack (Courtesy&colon; Armadillo Aerospace)

Armadillo Aerospace’s Pixel vehicle performs a hover test. An identical vehicle called Texel was wrecked in a crash landing on Saturday

(Image: Armadillo Aerospace)

The front-runner for a &dollar;2 million NASA competition to build mock lunar landers has lost one of its two main vehicles in a fiery crash. The company, Armadillo Aerospace, says it will enter a smaller vehicle instead, but outsiders say the upset will level the playing field and add suspense to the upcoming contest.

The Northrop Grumman Lunar Lander Challenge is designed to spur innovation in future vehicles that could take off and land vertically on the Moon. The event will be held on 27 and 28 October at the X Prize Cup in Alamogordo, New Mexico, US.

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Nine teams have signed up for the competition, but Armadillo Aerospace of Mesquite, Texas, US, is by far the leading contender for the prize. The company, led by Doom video game creator John Carmack, nearly won the 2006 contest, in which it was the only entrant.

The challenge has two ‘levels’ that involve a vehicle lifting off at one launch pad and hovering – for either 90 or 180 seconds, depending on the level – at an altitude of 50 metres as it moves to a second launch pad 100 metres away. Then the vehicle must do the same thing in reverse. If more than one vehicle achieves this, then the vehicle that can repeat it the greatest number of times in a given time period of time will win.

Armadillo has two main rockets, twin vehicles called Pixel and Texel. It plans to enter its better-tested Pixel into the more difficult level 2 contest, which carries a top prize of &dollar;1 million, and it had planned to enter Texel into the &dollar;350,000 level 1 contest.

But on Saturday, Texel burst into flames after it crash landed during a test. Its fuel and liquid oxygen tanks were so damaged in the impact that it would be easier to build a new vehicle from scratch than to repair Texel, says Armadillo test team member Phil Eaton.

Engulfed in flames

Rather than trying to build a new vehicle based on Texel’s design, however, Armadillo now plans to use an existing vehicle called Module 1 to vie for the prize. With two tanks compared to Texel’s four, Module 1 has less fuel capacity and cannot hover as long. But its makers say it is still capable of winning the level 1 prize.

“We ought to have things covered for the X Prize Cup for level 1 and level 2,” Eaton says.

When Texel was destroyed, Armadillo was testing an automatic system to shut down its engines. The system was designed to reduce bouncing when the vehicle lands, which had tended to occur when the engine was powered down by a human controller.

During the test, Texel lifted off and hovered without incident, then descended again and touched the ground. But it then rose again unexpectedly and began accelerating upward. “Crap, it’s going to fly into the crane, I need to kill it,” Carmack recalls thinking.

He hit the manual shutdown switch, turning off the vehicle’s engine in mid-flight. Texel was about 6 metres above the ground and fell like a stone. One of its fuel tanks broke open when it hit the ground, spewing fuel that ignited and engulfed the vehicle in flames. “It made a fireball that would make any Hollywood movie proud,” Carmack says.

A fire truck at the test site quickly doused the flames with water, and fortunately, no one was injured in the crash.

Faulty readings

Post-crash analysis has revealed what went wrong – the automatic shutdown that should have triggered when Texel first touched down did not occur. That’s because the computer was mistakenly told to expect a stronger signal from the touchdown sensor, beyond what it is actually capable of producing.

But the touchdown did have a big enough effect to jostle the onboard GPS unit that Texel relied on to track its motion. The disturbance caused faulty readings from the unit, confusing the vehicle.

“It thought that it was plummeting to earth very quickly, so it fired the engine to reduce the speed,” Eaton told New Scientist. “Well, it actually wasn’t going down, so this caused it to start going up very quickly.” That is when Carmack triggered the manual shutdown.

Although no one was harmed in the crash, Eaton says there are risks involved in rocket tests, underscored by the July explosion that killed three people at a test site for the pioneering commercial spaceflight company Scaled Composites in Mojave, California, US. “We try as hard as we can to eliminate those [risks] so that our team members are safe, but it doesn’t eliminate every possibility of something catastrophic,” Eaton told New Scientist.

Up the ante

But he says all three shutdown triggers meant to reduce the danger of the vehicle flying out of control worked as expected. In addition to Carmack’s manual shutdown command, the vehicle’s computer also sensed it was going astray and triggered an automatic shutdown at nearly the same instant, followed shortly by another manual shutdown command from another team member. Any of these three would have shut down the engine on its own.

Henry Spencer, a computer programmer and space enthusiast, thinks the lunar lander competition could be more interesting in light of the crash.

He notes that the front-runner for the first solo, non-stop transatlantic flight of an aircraft in 1927 was not Charles Lindbergh but Richard Byrd, “until he crashed on take-off, and just like that, was out of the race.” That left Lindbergh to win the &dollar;25,000 prize for the flight.

“This sort of thing is, of course, what helps make horse races,” he says of Texel’s demise.